Temperature regulating system



A 26, 1952 c. L. MERSHON 2,608,635

TEMPERATURE REGULATING SYSTEM Filed March 17, 1950 WITNESSES: INVENTOR Clorenice L. Mershon.

Patented Aug. 26, 1952 i U T DESI A E A E TEMPERATURE R GULATING SYSTEM Clarence L. vMershon, Lima, hio, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 17, 1950', Serial No. 150,2:65

3 Claims. (01. 219 2,o)

This invention relates to regulating systems, and in particular'to systems for regulating and controlling the temperature of windows for aircraft. This application is related to Serial No.

160,612, filed May 8; 1950, which has the same inventor and assignee as the present application.

An object of this invention is to provide in a regulating system for controlling the temperature of a window exposed'to various weather conditions, for obtaining a variable heating of the window to a predetermined temperature, the heating effect increasing as the window temperature approaches a predetermined temperature to bemaintained; I

Another object of this invention is to provide in a regulating system for controlling the temperature of a window exposed'to various weather conditions, for controlling the reactance of a saturable reactor in the power circuit tothe heating 'element for the window in accordance with the temperature of'the window and therebyeifect an increase in the heating efiect as the window temperature increases towards a predetermind temperature which is to be maintained.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawing, the single figure of which is a diagrammatic view of apparatus and circuits involved in teachings of this invention.

Referring to the drawing, this invention is illustrated by reference toa system for controllingthe temperature of a window pane H). The window pane i0 is of a well known sandwich type having the heating element (not shown)' imbedded therein disposed to be energized for effectively heating the window pane. 'Such window panes are illustrated in myPatent No. 2,462,207, issued February 22, 1949, and are more fully described in Technical Glass Bulletin No. of the Pittsburgh Plate Glass Company of Pittsburgh, Pennsylvania.

In order to supply current to the heating ele ment (not shown) of the window pane l0; a terminal I2 of th heating element is connected as by. aconductor I 4 to a terminal {6 of a source of power (not'sho'wmyanother terminal l8 of the heating element being disposed to be connected through the alternating current windings of a saturable reactor 22, conductor 24, and a contact member 26' of a contactor 28 to the other terminal' -30 of a'source (not shown) of alternating current supply. The contactor 28 is also. provided with an energizing winding 32 which is disposed to be energized to control the operation of the contactor 28 to and from a cuit closing position In order to control the energization "of the winding 32 of'the contactor 28, a polarized relay 34 is provided having a pivoted armature contact member 36 disposed to be operated into and out of engagement with a fixed contact member 38' for establishing an energizing circuit for the winding 32, This energizing circuit extends from one terminal represented by the positive symbol of a source of direct current power; through conductors 40 and 42, the armature contact" member 36 of thepolari'zed relay 34, fixed contactmember 38, the energizing winding 32, and con ductor 44 to the other terminal represented "by the'ne gative symbol of the direct current source of supply. The polarized relay 34 is of the 'usual construction, being provided with an energizing winding 46 which in this instance, is connected across the output terminals 48 and 50' of a resistance bridge or Wheatstone bridge circuit 52 to'be energized in accordance with the conditions of balance of the bridge circuit 52.

The resistance bridge circuit 52 is composed of a plurality of elements forming the legs thereof, and is connected at the input terminals 54 and 56 thereof through conductors 40 and respectively, to the source of direct current supply represented by the positive andnegative sym-, 3 bols'. In this embodiment, one leg of the resistance bridge circuit 52 includes a temperature sensitive element 58 formed of material lsuchfa'sl nickel, having a high temperature coefficient of resistance, the other legs of the resistance'bridge being formed of resistors 60, 62 and 64 of mate rial having a low temperature coeflicient of re;-,

sistance such as Advance metal. The temperature sensitive element 58 is disposed in juxtaposition with respect to the window pane iiljso that the resistance of the temperature sensitive element 58 will vary directly as the temperature of the window pane l0 varies. In practicefthe temperature sensitive element 58 is preferably imbedded between thelayers of glass forming the sandwich type of window pane It! so as .to

be directly affected by the temperature developed by the heating element (not shown) thewin dow pane Hi;

In order to vary the heating effect of the window pane ID as the temperature of the window pane is increased from a relativelylow temperature towards the temperature which is to;be maintained in the window pane Ill,- another bridge circuit 66 is disposed with its inputterminals 68 and Ill connected across the direct cur-j.

The other legs 80, 82 and 84 of' the resistance bridge 66 are preferably formed I 01' the material having a low temperature coefiicient of resistance so that the balance of the bridge circuit is directly afiected by the response of the temperature sensitive element 'Hl'to the temperature of the window pane l0; In practice, the resistance of the bridge circuit 66 is preferably so adjusted that when the window pane I0 is cold, there is only a slight unbalance in'jthe "bridge circuit 66. whereby a low output voltage is applied to the direct currentcontrol.

winding 16 of the saturable reactor 22.

Inoperat-ion, when heat is initially to beapplied to-the-windowpane Ill, the. window pane l0 generally is cold. Under such conditions, the

resistance. bridge circuit 66 is slightly unbalanced-- as-ireferred to hereinbefore, so that avery low voltage is applied to the direct current control winding 16 of the saturable reactor 22 and almost.

full-reactance of the saturable reactor 22 .is applied-t0 the energizing circuit for the heating ele-.

ment (not, shown) of the window pane l0. Under such; cold operating conditions'of the window panerlfl, the resistance bridge circuit 52 is also sounbalanced-that the polarized relay 34 is en-- ergizedi'toactuate the armature contact member 36 -into engagement with fixed contact member 38 ,to energize the winding 32 of the contactor 28 and actuate the contact member 26 thereof to acircuit closing position. Under such conditions-the heating element (not shown) is connected to the source of alternating current supply, but sincethe saturable reactor 22 has a high reactancathe voltage applied to the heating elementtnot shown) of the window pane I0 is maintained; at a low value.

Asenergyis thus supplied to the heating element (not-shown)- of the window pane L0, and

the temperature thereof increases, the resistanceof the temperature sensitive element 18 also increases i whereby a larger unbalance .of the bridge-circuit 66 is provided with the result that a largerfvoltage is applied tothecontrol windingi lfi ofthe saturable reactor 22. The increase in. current thus flowing in'the control winding Hi thereof tends to saturate the core of the saturable. reactor 22 to thereby reduce the reactance in series with the heating element (not shown) of the windowpane [0. In this manner, the voltageinitially applied to the heating element of the. cold: window pane H] is low and as the temperature of the window pane l8 gradually increases, the voltage applied also gradually.in-

creases.

ilhe resistance bridge 52 is initially so adjusted or designed. that for all temperature conditions of the window pane l 0 up to the temperature which is to be maintained, the resistance bridge 52 will be so unbalanced as to maintain the armature contact 'membersii of the polarized relay 34 in contact engagin member 38 to maintain the energizing circuit for the'winding 3 2 of the contactor 28. At such predetermined temperature for the Window pane l0, thePresistance bridge 65 is'so greatly unbalanced that suflicient current flows in the control winding 16 of the saturable reactor 22 to reduce the reactance of the winding 20 of the saturable reactor 22 to a very low value whereby practically full voltage is applied from the source of alternating current power to the heating element (not shown) of the window pane I0. I p

' As will be appreciated, after the temperature of the window pane in has reached the predetermined temperature which is to be maintained, under which conditions the reactance of the saturablereactor 22 is at a very low value, the

control of the temperature of the window pane l 0 is thereafter regulated by the response of the resistancebridge circuit 52 to changes in temperature of the window pane I 0. Thus, as the temperature of the:window pane I0 increases above the predetermined value which is to be maintained, the resistance of the temperature sensitive element 58 is so changed as to tend to effect a balance of the resistance bridge circuit 52.; Under such balancedconditions the armature contact member 36 of the polarized relay 34 is actuated to .a circuit opening position to interrupt the energizing circuit-ref the winding 32.

As-the winding 32-is deenergized, the. contact member 26 of the contactor 28 drops to a circuit openingposition to interrupt the energizing circuit for theheatingelement (not shown) of the,

window pane I0; Of course, if the temperature of the window pane Iii-tends to decrease from the predetermined value which is to bemaintained,

the balance of the resistance bridge'52 is so afiected that the polarized relay 34 is againsoenergized I as to again establish the energizing circuit for 32 of the;contactor 28;:to;

the energizing winding actuate contact member 26 thereof to a circuit closing position to establish the; .energization for theheating. element (not shown) of the win--, temperature of the -window dow pane lll, The pane it] is thus maintained at a predetermined temperature.

It is thus seen that thesaturable reactor-22 and the resistance bridge circuit 65 function to modulate or vary the heating effect of the window panel!) as it is being brought to a predetermined temperature so that when, the window pane 10 is cold the heating efiect is'less than when the temperature of the window panejapproaches the temperature which'is tolbe mainposition with the fixed contact tained. By controlling the heating eiTect of the window pane in this manner, a more uniform heating of the window pane in is obtained, and the slow gradual increase in the heating efiect eliminates damage to the spots in the Iwindow'pane when initially heated. The resistance bridges 52 and 66 thus cooperate very efiectively for controlling the heating effect. and after a predetermined temperature ,has'been' obtained, prevent overheating of the window pane. This control is obtained with standard components and the system described can be readily reproduced for obtaining the control. Iclaimasm-y invention:- ,1. In a system for associated therewith,

in combination, terminals for applying thereto a tionship with the resistor heating-element across the terminals, a relay for actuating" the contactor, a resistance bridge circuit having a tem-' p the bridge circuit in accordance with the temwindow caused by hot regulating the temperature of a Window having a resistor" heating element source of power, a variable" impedance means, a contactor for connecting the variable impedance means in series circuit rela perature of the window, the bridge circuit being in balance when the temperature of the window is at its regulated value and its output being connected to the relay to control its energization in accordance with whether the temperature of the window is above or below its regulated value, and another resistance bridge circuit connected to the variable impedance means and being only slightly unbalanced when the window is cold, said another resistance bridge circuit also having a temperature sensitive element disposed in juxtaposition to the window to control the balance of said another bridge circuit and thereby control the impedance of the variable impedance means in accordance with the temperature of the window to control the flow of current in the window heating element when the contactor is actuated to connect the window heating element to the source of power to thereby gradually increase the temperature of the window at apredetermined rate.

2. In a system for regulating the temperature of a window having a resistor heating element associated therewith, in combination, terminals for applying thereto a source of power, a saturable reactor having an alternating current winding and a direct current control winding for varying the impedance of the alternating current winding, a contactor for connecting the alternating current winding in series circuit relationship with the resistor heating element across the terminals, a relay for actuating the contactor, a resistance bridge circuit having a temperature sensitive element disposed in juxtaposition to the window to control the balance of the bridge circuit in accordance with the temperature of the window, the bridge circuit being in balance when the temperature of the window is at its regulated value and its output being connected to the relay to control its energization in accordance with whether the temperature of the [window is above or below its regulated value, and another resistance bridge circuit connected to the direct current control winding of the saturable reactor and being only slightly unbalanced when the window is cold, said another resistance bridge circuit also having a temperature sensitive element disposed in juxtaposition to the window to control the balance of said another bridge circuit in accordance with the temperature of the window and thereby control the impedance of the alternating current winding to gradually increase the current flow to the resistor heatin element at a predetermined rate when the contactor is actuated to connect the window heating element to the source of power.

3. In a circuit for regulating the temperature of a window pane having a heating element associated therewith, the combination comprising, terminals for applying thereto alternating current energy, a saturable reactor comprising an alternating current winding and a control winding for varying the impedance of the alternating current winding, a contactor for connecting the alternating current winding in series circuit relationship with the heating element across the terminals, a Wheatstone bridge one leg of which comprises a heat sensitive element disposed in juxtaposition to the window pane for controlling the balance of the bridge in accordance with the temperature of the window pane, a relay connected to the output of the bridge for actuating the contactor in response to an unbalance of the bridge to thereby maintain the temperature of the window pane at its regulated value, the bridge being in balance when the temperature of the window pane is at its regulated value, another Wheatstone bridge having a heat sensitive element also disposed in juxtaposition to the window pane for gradually further urrbalancing said another Wheatstone bridge as the temperature of the window pane increases, the output of said another Wheatstone bridge being connected to the control winding to control the impedance of the alternating current winding in accordance with the temperature of the window to thereby increase the temperature of the window pane at a predetermined rate when the contactor is actuated to connect the heating element to the terminals which have applied thereto alternating current energy, and circuit means for applying a substantially constant voltage to the inputs of the two Wheatstone bridges.

CLARENCE L. MERSHON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,948,372 Fitzgerald Feb. 20, 1934 1,991,248 Hartigan Feb. 12, 1935 1,995,404 Stoller Mar. 26, 1935 2,206,715 Burat et a1. June 2, 1940 2,429,827 Lamm Oct. 28, 1947 2,432,399 Edwards Dec. 9, 1947 2,462,207 Mershon Feb. 22, 1949 2,465,312 Mershon Mar. 22, 1949 2,556,065 Callender June 5, 1951 2,557,905 Burton et al. June 19, 1951 

